Apparatus for making electrical connections



June 1, 1965 R. F. COBAUGH 3,186,072

APPARATUS FOR MAKING ELECTRICAL CONNECTIONS Filed Aug. 19, 1963 4 Sheets-Sheet 1 June 1, 1965 F. COBAUGH APPARATUS FOR MAKING ELECTRICAL CONNECTIONS 4 Sheets-Sheet 2 Filed Aug. 19, 1963 3,186,072 APPARATUS FOR MAKING ELECTRICAL CONNECTIONS Filed Aug. 19, 1963 June 1 R. F. COBAUGH 4 Sheets-Sheet 3 June 1, 1965 R. F. COBAUGH 3,186,072

APPARATUS FOR MAKING ELECTRICAL CONNECTIONS Filed Aug. 19, 1963 4 Sheets-Sheet 4 United States Patent 0 3,185,072 APPARATUS FGR MAKING ELEETRIQAL QQNNECTHUNS Robert F. Cobaugh, Hershey, Pan, assignor to AMP incorporated, Harrisburg, Pa. Filed Aug. 19, 1963, Ser. No. 302,896 8 Claims. ('Jl. 29203} This invention relates to apparatus for making electrical connections between terminal posts and conductors.

In my co-pending application Serial Number 171,674, filed February 5, 1962, for Electrical Connections, there is disclosed a method and apparatus for electrically connecting a conductor to a terminal post by means of an open-sided clip which is adapted to embrace the post and to hold the conductor against its surface. in accordance with the principles of application Serial Number 17l,074, the wire is positioned with its axis extending transversely of the axis of the post and the clip is moved axially past the wire, over a mandrel which supports the clip, and onto the post. During its movement, the clip drags the end portion of the wire over the surface of the mandrel and onto the post. When the terminal clip comes to rest on the post, the end portion of the conductor is clamped by the web of the clip against the surface of the post with the adjacent portion of the conductor extending from beneath the clip and towards the other post towhich it is to be connected. The above identified application discloses suitable forms of terminal clips and apparatus for carrying out the invention as briefly described above. One suitable apparatus comprises a reciprocabl-e clip pusher which is movable over the mandrel and which has a recess or cavity at its leading end for holding the terminal clip being pushed onto the post. The clip pusher may be actuated by means of a pneumatic piston-cylinder, by electrical means such as a solenoid, or by a suitable manually actuated mechanical linkage.

The terminal clip wire connecting teclmique as described above is frequently used for the wiring of panelboards having a multiplicity of terminal posts extending therefrom. Such panelboards are used for making the numerous electrical connections required for relatively complex electrical and electronic systems such as control systems of various types, communications systems and computers. It is frequently necessary to electrically connect two or more conductors to each other on such paneboards and such connections are made by merely connecting each of the conductors to a single post. Thus, some of the terminal posts will have two or more terminal clips mounted thereon. It will be apparent that when a conductor is electrically connected to a terminal post which has a previously positioned clip mounted thereon, the second clip will be pushed on the post until it is adjacent to or against the first clip. in other words, the clip pushing tool pushes the second clip a shorter distance than the first clip was pushed. If the clip pusher is actuated by an actuating means having a stroke of fixed amplitude, such as a pneumatic piston-cylinder, the amplitude of the stroke must be sufficient to push the first clip the required distance below the end of the post. When the second clip is applied, this second clip will be pushed against the first clip and the clip pusher will be stopped from further movement by the first'clip prior to the time the clip pusher reaches the end of its stroke. lt has been found that under some circumstances, damage to the clips results when the second clip is moved against the first clip particularly if the clip pusher'is moving at a relatively high velocity and the second clip is slammed or impacted against the first clip. The present invention is directed specifically to the problem of the damage which can result to theterrninal clips wh'en a second or third clip is applied to a single terminal post by means of a clip applying tool 3,186,072 Patented dune l, 1955 having fixed stroke actuating means such as a pistoncylinder. 7

t is an object of the present invention to provide an improved apparatus for applying terminal clips to terminal posts to form electrical connections-between conductors and the terminal posts. A further object is to provide a clip applying tool comprising a clip pusher and a fixed stroke actuating means for the clip pusher and including means for preventing a second clip which is applied to .a terminal post from being impacted or slammed against a previously applied clip or clips. A further object of the invention is to provide a clip applying tool which is substantially foolproof in that the pushing force applied to the terminal clip is automatically relieved as soon as the clip moves against a previously applied clip whereby impact damage to the clips is avoided.

These and other objects of the invention are achieved in a preferred embodiment thereof comprising a reciprocable clip pusher for pushing a terminal clip along a predetermined path past a transversely extending wire, over a clip supporting mandrel, and onto a terminal post. The clip pusher is actuated by a pneumatic piston-cylinder having a fixed stroke, the amplitude of which is sufficient to push a clip to .a position adjacent to the base of the terminal post. The clip pusher is concatenated to the piston rod of the piston-cylinder by means of two separate couplings, one of which comprises a disengageable rigid coupling and the other of which comprises an overload release coupling. These two couplings are arranged in parallel relationship to each other relative to the path of transmission of thrust from the piston rod to the clip pusher. When both couplings are engaged, thrust is transmitted from the piston rod through the rigid coupling to the clip pusher and the overload release coupling is bypassed. Means are provided for automatically disengaging the rigid coupling during the forward stroke of the piston rod. Preferably, this disengageable rigid coupling is broken immediately after the terminal clip has been pushed from the mandrel and onto the free end of the terminal post so that during the remainder of the forward stroke, the thrust is transmitted only by the overload release coupling. The threshold thrust required to break this overload release coupling is sutliciently high to mainthe pusher and piston rod engaged as long as the clip being pushed does not encounter an impediment to its movement. This threshold thrust is, however, such that the coupling is broken as'soon as the clip being pushed engages an impediment which increases the resistance to its movement over the post. With this arrangement, the first clip which is applied to a terminal post can be pushed to a position adjacent the end of the post and the overload release coupling will not be broken. When a second or subsequent clip is applied to the same post, the coupling is broken as soon as the second clip moves against the first clip so that the clip pusher ceases to move although the fixed stroke piston rod is permitted to move until it reaches the end of its forward stroke.

One preferred embodiment of the invention is shown in the accompanying drawings in which:

FIGURE 1 is a perspective view of a pneumatically actuated hand tool embodying the principlesoi the invention.

ETGURE 2 is a sectional side view showing the forward end of the tool of FEGURE 1 which contains the clip pusher, the coupling between the clip pusher and the piston rod, and the clip feeding and transfer mechanism.

FIGURE 3 is aperspect-ive view showing the coupling blocks by means of which the clip pusher is coupled to the piston rod.

FIGURE 4- is a view similar to FIGURE 3 but showing the parts exploded from each other.

FIGURE 5 -is a top plan view taken along the lines 5-5 of FIGURE 2, of the coupling blocks.

FIGURE 6 is a sectional side view of the coupling blocks taken along the lines 66 of FIGURE 5.

FIGURE 7 is a view similar to FIGURE 6 but showing the positions of the parts after the disengageable rigid coupling between the piston rod and the clip pusher has been broken.

FIGURE 8 is a View similar to FIGURE 5 but showing the positions of the parts after the overload release coupling has been broken and illustrating the manner in which the piston rod is permitted to move relative to the clip pusher after the clip pusher has come to rest.

FIGURE 9 is a perspective view showing a short section of terminal clips in strip form.

FIGURE 10 is a sectional side view showing an electrical connection between a conductor and a terminal post by means of a terminal clip.

Referring first to FIGURES 9 and 10, one for-m of terminal clip for forming connections in accordance with my above-identified application, Serial Number 171,074, comprises a web 4 having sidewalls 6 extending laterally from its opposite sides. These sidewalls are cur-led towards each other and towards the web as shown at 8 so that each clip is adapted to embrace a terminal post and to hold the stripped end 14 of the wire against the surface of the post with the insulated portion of the wire emerging from the lower end of the clip which is adjacent to the surface of the panelboard. Advantageously an outwardly cupped insulation support It) is provided on the leading end of the web to support the insulation of the wire and to protect the stripped end from the imposition of tensile stresses. Terminal clips of this type are advant-ageously manufactured from flat metal strip stock by die stamping and forming techniques and produced in the form of a continuous strip.

FIGURES 1 and 2 show one type of pneumatically actuated hand tool for making electrical connections in accordance with the principles of the invent-ion described in my co-pending application Serial Number 171,074. The hand tool of FIGURES l and 2 is substantially similar, insofar as the clip feeding and clip moving mechanisms are concerned, to the hand tools shown and described in detail in application Serial Number 250,300, filed by Edwin Floyd, and the hand tool disclosed in my co-pending application Serial Number 300,542, for Apparatus for Connecting Wires to Terminal Posts. The clip feeding mechanism and other structural features previously disclosed in the above identified applications will be described only briefly below and to the extent necessary for an understanding of the instant invention which relates specifically to the manner in which the piston rod of the piston-cylinder is coupled to the clip pusher.

The tool of FIGURE 1 comprises a pair of handle covers 18 on the upper end of which a pair of frame plates 20, 22 are mounted. The clip pushing and clip feeding mechanisms are mounted between the frame plates as described more fully below. A pneumatic piston-cylinder 24 extends re-arwardly from the tool and a reel 2d of the terminal clip strip 2 is mounted above the piston-cylinder by means of a bracket 28.

A generally triangular mandrel block is mounted between the plates 20, 22 at the forward end of the tool by means of suitable fasteners 31 as shown. On its upper side, this mandrel block has a T-shaped mandrel 32 extending towards the forward end of the tool over which the terminal clips are adapted to be pushed. A wire receiving recess 34 extends downwardly into a mandrel block through the mandrel projection 32 and an upwardly sloping groove 46 extends from this recess towards the tOp surface of the mandrel. This groove facilitates the severing of the insulation and the withdrawal of the conducting core of the wire from a severed section of insulation as the terminal clip moves over the mandrel and onto a terminal post. In use, the tool is positioned against the post with the end of the post disposed against the end 48 of the mandrel and with the sides of the post held between resilient fingers Sti extending from spring plates 49 on each side of the mandrel block.

Advantageously, a pivoted arm 36 extends along and above the mandrel 32 and has a slot extending inwardly from its forward end in which an L-shaped dog is pivotally mounted. This dog has a depending arm which is biased leftwardly in FIGURE 2 by means of an helical spring 43 which serves to lightly clamp the wire in the recess after insertion. In order to facilitate insertion, conical depressions 42 are provided on each side of the slot in the leading end of the arm 36. The arm 36 is pivotally mounted on its righthand end as shown at 38 to a block 40 contained between the frame plates 20, 22. The terminal clips in strip form are fed over the surface 64 of a bar 66 secured to the side plate 22 and onto a T-shaped projection on the upper end of a reciprocable transfer slide 52. This slide is guided by vertical motion as viewed in FIGURE 2 between the mandrel block 30 and a guide block 54. Movement is imparted to the transfer slide by means of a rocker arm 60 having a pin 58 in its lefthand end which is received within a slot 56 in the transfer slide. The rocker arm is pivotally mounted intermediate its ends at 62 so that upon clockwise motion or rocking of this rocker arm, the transfer slide will be moved upwardly in FIG- URE 2 and the leading terminal of the strip will be raised until it is in alignment with the mandrel 32 on the mandrel block. During upward movement of the transfer slide, this leading terminal clip is sheared from the strip by means of a shearing edge indicated at 53.

The rocker arm 60 is rocked about its pivotal axis 62 by means of a block 90 mounted on the end of the piston rod 84 and a spring 91 mounted on the block and having an arm extending towards the rocker arm. FIGURE 2 shows the posit-ions of the parts after the completion of an operating cycle and with the transfer in its raised position. Upon leftward movement of the piston rod 84, the rocker arm is first swung in a counterclockwise direction by the arm of the spring 90 which moves over the upper surface of rocker arm 60. Towards the end of the leftward or forward stroke of the piston rod 84, the underside of the block 90 engages the lefthand end of rocker arm 60 to lower it through the final portion of its downward travel and to precisely position the clip supporting projection on the upper end of this arm in alignment with the strip of terminals which is fed leftwardly during the forward stroke of the piston rod as described below. Upon rightward movement of the piston rod (i.e. the return stroke), the rocker arm 60 is swung in a clockwise direction by the spring arm 91 to raise the transfer slide 52 until the parts occupy the position of FIGURE 2.

The strip of terminal clips is fed over the upper surface 64 of a block 66 secured to the frame plate 22 by means of a feed pawl which extends through a slot in the forward end of the block and engages the underside of the strip of clips. This feed pawl is pivotally mounted on a pin 70 and biased in a clockwise direction by a torsion spring as shown. The pin 70 extends from a slide block 72 which is mounted in a slot in the block 66 and resiliently biased rightwardly in FIGURE 2. The spring (not shown) which biases the block 72 is contained within the slot in the block 66, the arrangement being functionally similar to the corresponding arrangement of the parts in the above identified Floyd application Serial Number 250,300. During the forward stroke of the piston rod 84, the block engages the slide block 72 to move this block leftwardly and advance the terminal strip until the leading clip thereof is positioned on the upper end of the transfer slide.

An individual terminal clip is pushed leftwardly in FIG- URE 2 from the transfer slide over the mandrel and past the wire by means of a reciprocable clip pusher 86 having a recess on its leading end 82 which surrounds the leading clip and pushes it leftwardly. On its righthand end, this clip pusheris coupled to the piston rod 84 of the pistoncylinder 24 by means of a pair of coupling blocks 86, 88. The block 86 is rigidly connected to the piston rod 84 by means of a flange member 92 which extends from the camrning block 94 on the end of a piston rod. Flange 92 has a laterally directed ear 93 which is received within a complementary opening 94 in the block 86. It will thus be apparent that the coupling block 86 moves leftwardly as viewed in FIGURE 2 for the full stroke of the piston rod 84 and that this block will remain coupled to the piston rod for the entire cycle. 7

Block 86 has a guide channel 96 onitsupper side which extends parallel to the axis of the piston rod 84 and the path of reciprocation of the clip pusher 80. The coupling 88 is slidably received within this. channel so that relative motion is permitted between the two blocks 86, 83. An ear 98 extends leftwardly from block 88 and beyond the lefthand side of the channel 96. The rearwardly facing side of this ear is normally engaged by the upwardly directed end 100 of a latch arm 102 pivotally' mounted at 104 on a pin extending from the lefthand side of the block 86 as viewed in FIGURE 4. A torsion spring 106 mounted on the block 86 normally biases the latch arm 102 in a clockwise direction as viewed in FIGURE 7 so that the upwardly directed end 100 of the latch arm will normally be maintained in engagement with the ear 98 of the block 88. It will be apparent that the coupling comprising this latch arm 102 and ear 98 constitutes a disengageable rigid coupling between the two blocks 86, 88 and that the latch arm will transmit the full thrust of the piston rod 84 to the pusher 80 so long as this coupling remains engaged.

The lefthand end of the latch arm 102 is provided with a sloping cam surface 108 which is engaged by a fixed camming block 110 mounted on the side plate 22. The location of this camming block 110 is advantageously such that the latch arm 102 will be swung in a counterclockwise direction as viewed in FIGURE 6 and the rigid coupling between the two blocks will be disengaged as shown in FIGURE 7 at about the same time, as or shortly after, the terminal clip has been pushed from the mandrel 32 onto the terminal post.

The block 88 is also coupled to the block 86 by an additional coupling means of the overload release type, that is to say a couplingwhich will transmit thrust up to a given level but which will be automatically broken if the thrust exceeds that level. This coupling comprises a roller 112 mounted on ap'ivotal axis in the bifurcated end 113 of a lever 114 which is pivotally mounted on the upper surface of the block 86 and on the lefthand side of the channel 96 arr/awed in FIGURE 4. Arm 114 is resiliently biased by means of a spring 112 towards an upstanding flange 118 of the block 88 and the roller 112 is normally urged into a groove 116 on the side of the flange 118. Spring 112 is contained in a hole in an upstanding projection 124 on the block 86, a set screw being provided in this hole to permit adjustment of the force exerted by the spring 118 and, therefore, the breaking force of the overload release coupling. The surface of the flange 118 slopes downwardly relative to the groove 116 so that after the roller ha moved relatively out of the groove 116 the block 86 can be moved leftwardly as viewed in FIGURE 3 relative to the block 88.

In use, the stroke of the piston rod 84 will normally be set such that a first clip applied to a terminal post will be moved to the lower end or substantially to the lower end of the post when the piston rod reaches the end of its stroke. has moved onto the post, the rigid disengageable connection between the blocks 86, 88 will be broken as described above when the clip moves onto the post but the overload release coupling will remain unbroken since the clip will not encounter excessive resistance to its movement. When a second, third, or subsequent clip is moved onto the post, to make an additional connection Under such circumstances, and when this clip to the same post, the rigid coupling will again be broken when the clip moves onto the post and the overload release coupling will remain engaged until the second clip moves against the first clip. At that time, the overload release coupling will be automatically broken thus relieving the thrust of the piston rod from the second clip while the piston rod completes the remainder of its stroke. After the overload release coupling has been broken, the parts will occupy the positions shown in F1- URE 8, with the block 88 extending rearwardly beyond the rearward end of the block 86.

During the return stroke of the piston rod, the blocks 86, 88 will remain in the relative positions'of FIGURE 8 until the end of the return stroke is reached. Immediately before the end of the return stroke, the rearwardl'y facing side of the block 88 will come into engagement with a forwardly facing surface '74 of a block i6 which is integral with the block 66. The block 88 will thus be stopped from further rearward movement and the block 86 will continue to move rearwardly until the two blocks are in the relative positions of FIGURES 3, 5 and 6.

A salient advantage of the invention is that the relatively high thrust is transmitted from the piston rod through the rigid coupling 98, 10%), 102 of the coupling blocks and to the terminal clip during the portion of the cycle when a high thrust is required, that is while the clip is being pushed over the mandrel and past the wire. During this portion of the cycle, the clip encounters a relatively high resistance to travel since it must push the wire against the sides of the opening 34 in the mandrel, drag the core of the wire from the end portion of insulation, and iron the stripped end of the wire against the surface of the mandrel. Upon disengagement of this rigid coupling, the maximum thrust which can be transmitted to the clip is limited, however, by the force required to break the overload release coupling. This coupling is automatically broken as soon as the clip moves against a previously applied clip and the possibility of damage is thereby obviated.

A further advantage of the invention is that the piston rod is permitted to travel the full length of it pre-set stroke although the clip pusher travels a lesser distance where a second or subsequent clip is being applied to a post. This feature is of importance in the above-described type of tool for the reason that the full stroke of the piston rod is required to elfect the strip feeding and transferring operations. In other words, if the piston rod were not permitted to complete its forward stroke, the transfer slide would not be lowered and/or the terminal strip would not be fed by pawl 65 a distance sufiicient to position the leading terminal on the transfer slide. The invention thus permits a fixed stroke actuator (the piston rod) to actuate two separate mechanisms, one of which (the clip pusher) must have a variable or indeterminate stroke and the other of which (the camming block 95)) must have a fixed stroke.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is olfered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

I claim:

1. In a device for pushing a terminal clip onto a terminal post and comprising a clip pusher reciprocable along a predetermined path and actuating means for reciprocating said clip pusher, the improvement comprising: 7

a disengageable rigid coupling between said actuating means and said clip pusher, an overload release coupling between said actuating means and said clip pusher, said couplings being in parallel relationship to each other relative to the path of transmission of thrust from said actuating means to said clip pusher whereby, said clip pusher and said actuating means are positively coupled while said disengageable rigid coupling is engaged, and means for disengaging said rigid coupling during forward movement of said clip pusher while a clip is being pushed onto a terminal post whereby, during a final portion of said forward stroke of said clip pusher, said pusher is coupled to said actuating means only by said overload release couplings, said clip pusher being automatically disengageable from said actuator when the resistance to movement of said clip exceeds the disengaging force of said overload release coupling.

2. In a device for pushing a terminal clip onto a terminal post and comprising a reciprocable clip pusher and actuating means for reciprocating said clip pusher, the improvement comprising: an overload release coupling between said clip pusher and said actuating means, said overload release coupling being disengageable upon imposition of a thrust of predetermined magnitude on said clip pusher and permitting movement of said actuating means relative to said clip pusher after imposition of said thrust, a nonyieldable disengageable coupling between said actuating means and said clip pusher, said couplings being arranged in parallel relationship relative to the direction of thrust transmission from said actuating means to said clip pusher, and disengaging means for disengaging said nonyieldable coupling during the forward stroke of said clip pusher and prior to the end of the forward strok of said actuating means whereby, during the final portion of said stroke of said clip pusher, said overload release coupling is broken if said clip encounters resistance to travel on said terminal post and said actuating means is permitted to complete its forward stroke.

3. Apparatus as set forth in claim 2 wherein said overload release coupling comprises a resiliently urged detent coupling.

4. Apparatus as set forth in claim 2 wherein said nonyieldable coupling comprises a latch means and said disengaging means comprises camming means engaged by said latch means.

5. In a device for pushing a terminal clip onto a terminal post and comprising a reciprocable clip pusher and a reciprocable actuator for actuating said clip pusher, the improvement comprising: an overload release coupling and a disengageable rigid coupling between said clip pusher and said actuator, said couplings being arranged in parallel relationship to each other relative to the path of thrust transmission from said actuator to said clip pusher, cam means for disengaging said rigid coupling at an intermediate stage of the clip pushing stroke of said clip pusher, and means for reengaging said rigid coupling during the return stroke of said clip pusher whereby, during the final portion of said clip pushing stroke, said overload release coupling only transmits thrust from said actuating means to said clip pusher, and said overload release coupling is broken if said clip moves against a previously applied clip on said post thereby to permit completion of the forward stroke of said actuator without transmission of thrust to said clip.

6. Apparatus as set forth in claim 5 including a pair of coupling blocks, said couplings being mounted on, and effective between, said coupling blocks, said coupling blocks being movable relative to each other after disengagement of both of said couplings, one of said blocks being rigidly concatenated to said clip pusher and the other of said blocks being rigidly concatenated to said actuator.

7. Apparatus as set forth in claim 5 including clip feeding means for feeding a strip of terminal clips during each reciprocation of said actuator, said clip feeding means being actuated by said actuator.

8. In a device for applying terminal clips to terminal posts comprising a reciprocable clip pusher and a re ciprocable piston rod for actuating said clip pusher, the improvement comprising: reciprocable terminal feeding means for feeding a strip of said terminal clips, means on said piston rod for engagement with said terminal feeding means during the final portion of the forward stroke of said piston rod thereby to feed said strip during said final portion of said stroke, a disengageable rigid coupling between said piston rod and said clip pusher, an overload release coupling between said piston rod and said clip pusher, said couplings being arranged in parallel relationship relative to the path of thrust transmission from said piston rod to said clip pusher, and means for disengaging said rigid coupling during the forward stroke of said piston rod whereby, during the final portion of said forward stroke, thrust is transmitted from said piston rod to said clip pusher through said overload release coupling only, and said overload release coupling is broken if said clip moves against a previously applied clip on said post thereby to permit said piston rod to complete its forward stroke and actuate said feed means while said clip pusher remains stationary.

References Qited by the Examiner UNITED STATES PATENTS 2,891,305 6/59 Waltke 29-206 3,074,155 1/63 Cootes et al. 29--206 WI-IITMORE A. WILTZ, Primary Examiner.

THOMAS H. EAGER, Examiner. 

1. IN A DEVICE FOR PUSHING A TERMINAL CLIP ONTO A TERMINAL POST AND COMPRISING A CLIP PUSHER RECIPROCABLE ALONG A PREDETERMINED PATH AND ACTUATING MEANS FOR RECIPROCATING SAID CLIP PUSHER, THE IMPROVEMENT COMPRISING: A DISENGAGEABLE RIGID COUPLING BETWEEN SAID ACTUATING MEANS AND SAID CLIP PUSHER, AN OVERLOAD RELEASE COUPLING BETWEEN SAID ACTUATING MEANS AND SAID CLIP PUSHER, SAID COUPLINGS BEING IN PARALLEL RELATIONSHIP TO EACH OTHER RELATIVE TO THE PATH OF TRANSMISSION OF THRUST FROM SAID ACTUATING MEANS TO SAID CLIP PUSHER WHEREBY, SAID CLIP PUSHER AND SAID ACTUATING MEANS ARE POSITIVELY COUPLED WHILE SAID DISENGAGEABLE RIGID COUPLING IS ENGAGED, AND MEANS FOR DISENGAGING SAID RIGID COUPLING DURING FORWARD MOVEMENT OF SAID CLIP PUSHER WHILE A CLIP IS BEING PUSHED ONTO A TERMINAL POST WHEREBY, DURING A FINAL PORTION OF SAID FORWARD STROKE OF SAID CLIP PUSHER, SAID PUSHER IS COUPLED TO SAID ACTUATING MEANS ONLY BY SAID OVERLOAD RELEASE COUPLINGS, SAID CLIP PUSHER BEING AUTOMATICALLY DISENGAGEABLE FROM SAID ACTUATOR WHEN THE RESISTANCE TO MOVEMENT OF SAID CLIP EXCEEDS THE DISENGAGING FORCE OF SAID OVERLOAD RELEASE COUPLING. 